The high-voltage glass fiber electroscope can not only check whether the conductor is charged, but also check the chargeability of the conductor. The conductor to be inspected is directly contacted with the metal ball of the high-voltage glass fiber electroscope or the two are connected by a wire, and it is judged whether the conductor is charged if the gold foil of the electroscope is opened. It is also possible to bring the conductor to be inspected into contact with the electroscope only to be close to the metal ball. If the conductor is charged, due to the electrostatic induction, the metal ball and the gold foil of the electroscope may respectively induce a different kind of electric charge to open the gold foil.

Then let the metal ball of the high-voltage glass fiber electroscope that has been positively charged be close to the conductor to be inspected. If the angle of the gold foil of the electroscope becomes larger, the conductor to be inspected is positively charged; if the angle of the gold foil of the electroscope is small , indicating that the conductor being inspected is negative or not charged. In this case, the conductor to be inspected can be brought close to the metal ball of the electroscope that is known to be negatively charged. If the angle of the gold foil becomes large, it can be confirmed that the conductor to be inspected must be negatively charged.

In addition, high-voltage glass fiber electroscopes can also be used to compare the potential of different conductors. It is only necessary to connect the metal balls of the same uncharged electroscope to the positively charged conductors A and B, respectively, to observe the size of the gold foil opening angle, and the potential of the connected conductor is high when the opening angle is large. If both conductors are negatively charged, the potential of the connected conductor is low when the opening angle is large.